There is no way to filter insource:/"<big></big>"/, for example. Filters for regex are very important to have.
The search "big big" will not look insource, so cannot act as a filter. (But it can find repeating words.)
The search insource:"big" and insource:"big big big" are equivalent, and a weak filter.
Unlike "big big big", which uses proximity zero, insource turns ''off'' proximity.
If insource at least had proximity zero, it could find phrases that would greatly increase the filtering needs of regex.
As it is the quotes are misleading, as insource cannot even find two words next to each other. Insource:"big big" is the same as insource:big insource:big. i is the inability to find repeating words.
Maybe it's just a feature request, but we're talking about supporting a rare public tool, regex. These things would run much much faster if they had the ability to filter word phrases.
Insource should at least set proximity to zero.